The present invention relates generally to clutch release-actuating hydraulic apparatus, and more particularly, to construction in order to improve wear-resistance of a hydraulic fluid chamber within a cylindrical housing of the hydraulic apparatus, in which a piston is operative in actuating clutch release.
In clutch release actuation, it is known to drive the clutch diaphragm spring to release the clutch utilizing hydraulic pressure via hydraulic release-actuating apparatus. One type of clutch release-actuating hydraulic apparatus consists chiefly of a cylindrical housing containing a piston which axially drives a clutch release bearing that is in contact or connection with the radially inward margin of the diaphragm spring.
The cylindrical housing is disposed encircling the transmission shaft of a motor vehicle power train. Double-walled, it thus defines a tubular fluid chamber which extends axially and is open-ended toward the clutch. The cylindrical housing fluid chamber contains an axially movable tubular piston, and a sealing member is provided on the piston for sealing piston-driving hydraulic fluid within the fluid chamber. In current practice, in order to reduce weight and decrease production cost, the cylindrical housing is made of a resin-based material reinforced with glass fiber.
During operation of the hydraulic clutch release-actuating apparatus, the piston is driven under hydraulic pressure on the piston sealing member to slide axially in the tubular fluid chamber. The sealing member as fit against the bore of the fluid chamber will In the course of operation subject the resin-based cylindrical housing to wear. Consequently, glass fiber in the resin may in some cases become exposed along the fluid chamber bore surface, damaging the sealing member. Sealing member damage thus leads to hydraulic fluid leakage, decreasing the life of the hydraulic clutch release-actuating apparatus.